1. Field of the Invention
The present invention relates to real-time in-situ monitoring of semiconductor processing. The invention uses infrared spectroscopy to monitor the substrate and the gaseous environment during a process.
2. Background of the Invention
Advanced process control that involves in-situ process monitoring and fault detection in semiconductor manufacturing is essential for reproducible production of complex structures. Introduction of new materials and smaller dimensions into integrated circuits results in the need for improved process monitoring to assure process compliance and cost reduction.
In typical etching and film deposition processes, the wafer parameters are measured after the processing steps using test wafers. If the measured parameters are not within the desired tolerances, the process parameters are adjusted and more test wafers are run and measured to verify the corrective measures. This method of post-process analysis is time consuming, inefficient, and becomes increasingly more expensive as the wafer size increases. In addition to manufacturing runs, process development and yield ramping increase the number of test wafers that require post-process analysis.
These drawbacks can be reduced using real-time tool and process monitoring. In order to minimize the number of wafers that are run on a faulty process, it is necessary to know if critical parameters are outside specifications during processing. If a process is stopped for troubleshooting, a wafer can be examined ex-situ for physical properties such as film thickness, density and composition. The use of real-time process monitoring will not eliminate the need for conventional ex-situ metrology, but will allow better process control and reduce the number of test wafers.
Real-time monitoring during etching and film deposition steps should (1) yield detailed information on the various chemical components in the gaseous environment and (2) in many cases, preferably also offer means for monitoring and analyzing chemical species on the substrate surface. The acquired data can be used to improve the process by optimizing process conditions, detecting trends of departure from target values and allow early recognition of a possible catastrophic failure of the process equipment. In addition to etching and film deposition processes, chamber cleaning and chamber conditioning processes require in-situ monitoring for improved process control.
A variety of spectroscopic methods have been applied to real-time process monitoring. These analytical methods allow qualitative and quantitative analysis of the gaseous chemical species through the use of techniques such as mass spectroscopy (MS) and optical emission spectroscopy (OES). These techniques provide information on the identity and concentration of gaseous species during the manufacturing process, which in turn can be correlated to various physical properties of the processed substrates.
OES is a widely used method for process monitoring and control in semiconductor processing. OES is a non-invasive technique that has an extremely wide dynamic range and can perform process control (e.g., endpoint detection, etch rate, or partial pressure control) and diagnostics concurrently. However, it cannot be used in non-plasma processes such as film deposition, and the optical emission spectrum from plasma processes can be very complicated. Furthermore, OES does not provide direct information about the substrate during a process step.
The aforementioned disadvantages using post-process analysis show that there is a need for non-invasive methods for monitoring of semiconductor processes that allow for comprehensive analysis of the gaseous environment and the substrate during a process step. The real-time results are correlated to various physical properties of the substrates and can reduce the use of test wafer reiterative monitoring methods.